The present invention provides an improvement in the operation of a centrifuge employing the teaching of my co-pending applications Ser. Nos. 831,055 and Ser. No. 831,056 now U.S. Pat. Nos. 4,640,770 and 4,639,320, respetively. The teachings of these applications enable a gimbal-mounted centrifuge to transit the critical speeds of rotation of a centrifuge with little transfer of energy to the gimbal-like structure in which the rotor is mounted, and provide the structure necessary to successfully operate a high speed overhung bowl centrifuge, consequently these applications are incorporated herein by reference.
In a centrifuge of the type with which my invention is intended for use, the rotating elements are dynamically balanced such that at high speed operation, above the critical speeds, the elements tend to rotate about their geometric longitudinal axis and develop a moment of inertia of WK.sup.2, where W is the mass (although weight is used in some calculations for simplicity) and K is the radius of gyration of the elements about the axis. When a quantity of centrifuge load material is placed within the centrifuge bowl, the distribution is likely to be unbalanced, thus the unbalanced load causes a radial deviation of the rotating system which causes the system to rotate about a dynamic axis. The radial deviation of the spinning mass results in gyroscopic torque being applied to the system. Thus, the system is subjected to competing stresses which yield a reactance on the gimbal-like mounting system. If this reactance or force is excessive, the gimbal-like mount is soon destroyed.
The deviation of the dynamic axis of rotation from the geometric axis of the rotating system has long been a concern of centrifuge designers, however, a satisfactory solution which will minimize the effects of an unbalanced condition on a gimballed centrifuge is not previously known.
Numerous patents have issued on dynamic balance systems for centrifugal extractors, such as washing machines and the like, wherein the rotor is mounted in fixed bearings. Some of these such as U.S. Pat. Nos. 2,420,592 and 3,683,647 use movable members mounted in association with the tub or bowl which are said to automatically compensate any unbalanced load. The most pertinent reference known to me is U.S. Pat. No. 3,362,198 wherein a balancing ring is used to counter dynamic imbalance in a loaded clothes washer, however, the rotator is not gimbal mounted and the machine disclosed therein operates under considerably different constraints than does my centrifuge. Most notably the balance ring of the '198 patent is not designed for use with a gimballed system, nor at the speeds at which my centrifuge operates. Furthermore, from the disclosure, it appears that the balance ring is quite massive relative to the remainder of the system, contrary to my invention as is hereinafter disclosed.